[dyncall] next shot at fixing the build on Strawberry Perl

Should work universally, but testing on OSX would be appreciated.
OSX 64 bit target for NativeCall
Remove stray blanks
Rolled QAST::Operations.add_hll_unbox calls into loop
Avoid a circularity; pmichaud++ for noticing.
Toss current container spec config op.

Not used in NQP itself, and we'll be changing how container stuff is
handled.
Start replacing container spec approach.

This is the minimum needed to get NQP to build and pass its tests again
with the data structure updates. Still needs some more infrastructure
before we can start updating Rakudo to use this new approach.
Don't decontainerize type objects.
Add container spec registry and code_pair spec.

The registry keeps track of different containerization strategies we
have. Implemented one that relies on a pair of code objects (a fetch
and a store), which provides one aspect of the previous functionality.
Deserialization for new container support.
Add new nqp::setcontspec and an nqp::assign op.
Some tests for the new container stuff.
Fix a replace-o.
Add nqp::assignunchecked(...).

Used for the case when the compiler (probably the optimizer) already
concluded that the assignment is safe.
Test nqp::assignunchecked op.
Provide a way for libs to register containers.

This means that Rakudo will be able to set up its scalar handling.
Add some documentation about signature argument to pirop_mapper.
Store REPR data offset in STables data also.

This makes it much easier for anything that wants to try and work out
sizing/layout before deserializing objects.
Add nqp::x_posixerrno
Add test for nqp::x_posixerrno and pir::const::POSIX_*